Tumbleweed36

First, I would try clearing the CMOS and see if that helps you to get in to the computer. If you do, then do a system restore to get back to when it worked.

Second possible solution:

If that does not help, then most likely you might have a boot.ini file that is corrupt. Here are some general comments about that issue:

When booting up to Windows XP you may get an error that reads: "Unmountable Boot Volume".

This is probably because your boot.ini file is messed up. Here is a possible remedy:

You can boot to the XP cd and when you see the "Welcome to setup" message, press the letter R.
You will then get a DOS prompt.
Then type: chkdsk /p [enter]
When that is done type: fixboot [enter]
Type: Y at the next prompt [enter]
Then type: exit [enter]
The system will now reboot into Windows.

If for some reason that didn't work, you can boot to the recovery console (example above).
Type: "chkdsk /r" [enter]
When done type: exit [enter].
This takes a bit longer, but the system should boot back into Windows.